Anything in production is legacy; I'm pretty sure it happens as soon as the code is shipped regardless of who wrote it.
Maybe they stick around for a while, maybe they move on to another job, but they were THERE at some point. They have a name. You can ask them questions about what they did. And hey, they still exist in the real world too, so you can get in touch with them even after they leave if you need to.
AI powered development is like a guy shows up, gets hired for 90 seconds, writes part of a feature, and dies instantly once the code hits the screen.